Universe Tenth Edition Roger Freedman • Robert Geller • William Kaufmann III Universe Tenth Edition Chapter 21: Black Holes

By reading this chapter, you will learn 21-1 The main ideas of Einstein’s special theory of relativity 21-2 How Einstein’s general theory of relativity describes the nature of gravitation 21-3 The evidence for black holes in binary star systems 21-4 How the sudden formation of black holes can explain the mysterious gamma-ray bursts 21-5 How astronomers have detected supermassive black holes at the centers of galaxies 21-6 The simple structure of a nonrotating black hole 21-7 How just three numbers completely describe the properties of a black hole 21-8 What it might be like to approach a black hole 21-9 How black holes evaporate over time

21-1: The special theory of relativity changes our conceptions of space and time The Speed of Light is the Same to All Observers

The Speed of Light is the Same to All Observers

The Speed of Light is the Same to All Observers

The Speed of Light is the Same to All Observers

21-2: The general theory of relativity predicts black holes The Equivalence Principle

The Equivalence Principle

The Gravitational Curvature of Spacetime

The Gravitational Curvature of Spacetime

The Gravitational Deflection of Light

The Gravitational Deflection of Light

The Precession of Mercury’s Orbit

The Precession of Mercury’s Orbit

The Gravitational Slowing of Time and the Gravitational Redshift

The Gravitational Slowing of Time and the Gravitational Redshift

The Gravitational Slowing of Time and the Gravitational Redshift

The Gravitational Slowing of Time and the Gravitational Redshift

The Formation of a Black Hole

The Formation of a Black Hole

Curved Spacetime around a Black Hole

Curved Spacetime around a Black Hole

21-3: Certain binary star systems probably contain black holes X-Rays Generated by Accretion of Matter Near a Black Hole

X-Rays Generated by Accretion of Matter Near a Black Hole

The Environment of an Accreting Black Hole

The Environment of an Accreting Black Hole

21-4: The most intense radiation bursts in the universe may be caused by the formation of black holes Gamma Ray Bursts

Gamma Ray Bursts

The Host Galaxy of a Gamma Ray Burst

The Collapsar Model of a Long-Duration Gamma Ray Burst

21-5: Supermassive black holes exist in the centers of most galaxies A Supermassive Black Hole

An Intermediate-mass Black Hole?

21-6: A nonrotating black hole has only a “center” and a “surface” The Structure of a Nonrotating (Schwarzschild Black Hole

Black Hole “Urban Legends”

Black Hole “Urban Legends”

21-7: Just three numbers completely describe the structure of a black hole The Structure of a Rotating (Kerr) Black Hole

A Rotating Supermassive Black Hole

The View Approaching a Black Hole

21-8: Falling into a black hole is an infinite voyage Effect of a Black Hole’s Tidal Force on Infalling Matter

21-9: Hawking radiation and black hole evaporation Hawking Radiation and Evaporation of a Black Hole

Hawking Radiation and Evaporation of a Black Hole

Key Ideas The Special Theory of Relativity: This theory, published by Einstein in 1905, describes how measurements of lengths and durations of time depend on the motion of an observer and can appear different to different observers. The speed of light is the same to all observers, no matter how fast they are moving. An observer will note a slowing of clocks and a shortening of rulers that are moving with respect to the observer. This effect becomes significant only if the clock or ruler is moving at a substantial fraction of the speed of light. Space and time are not wholly independent of each other, but are aspects of a single entity called spacetime.

Key Ideas The General Theory of Relativity: Published by Einstein in 1915, this is a theory of gravity. Any massive object causes space to curve and time to slow down, and these effects manifest themselves as a gravitational force. These distortions of space and time are most noticeable in the vicinity of large masses or compact objects. The general theory of relativity is our most accurate description of gravitation. It predicts a number of phenomena, including the bending of light by gravity and the gravitational redshift, whose existence has been confirmed by observation and experiment.

Key Ideas The general theory of relativity also predicts the existence of gravitational waves, which are ripples in the overall geometry of space and time produced by moving masses. Gravitational waves have been detected indirectly, and specialized antennas are under construction to make direct measurement of the gravitational waves from cosmic cataclysms. Black Holes: If a stellar corpse has a mass greater than about 2 to 3 M, gravitational compression will overwhelm any and all forms of internal pressure. A black hole has an escape speed greater than the speed of light. Nothing, not even light, can escape a black hole once it crosses into a black hole’s event horizon.

Key Ideas Observing Black Holes: Black holes have been detected using indirect methods. Some binary star systems contain a black hole. In such a system, gases captured from the companion star by the black hole emit detectable X rays. The emission comes from outside the event horizon. Many galaxies have supermassive black holes at their centers. These are detected by observing the motions of material around the black hole.

Key Ideas Gamma-Ray Bursts: Short, intense bursts of gamma rays are observed at random times coming from random parts of the sky. By observing the afterglow of long-duration gamma-ray bursters, astronomers find that these objects have very large redshifts and appear to be located within distant galaxies. The bursts are correlated with supernovae, and may be due to an exotic type of supernova called a collapsar. The origin of short-duration gamma-ray bursters is unknown.

Key Ideas Properties of Black Holes: The entire mass of a black hole is concentrated in an infinitely dense singularity. A black hole has only three physical properties: mass, electric charge, and angular momentum. A rotating black hole (one with angular momentum) has an ergoregion around the outside of the event horizon. In the ergoregion, space and time themselves are dragged along with the rotation of the black hole.

Key Ideas Black holes emit Hawking radiation from a quantum physics process that occurs just outside of their event horizons. Black holes have temperatures and their Hawking radiation is emitted like the blackbody radiation that is emitted by any object with a temperature. Black holes can evaporate, but in most cases at an extremely slow rate unless the black holes are very small